C-C versus C-N annulation reactions of 2-alkyl-2-oxazolines and 2-alkyl-2-thiazolines: A simple synthesis of novel 3-aminoindene, phthalimidine, pyrrolidine, and piperidine derivatives

The effect of various aromatic and aliphatic dielectrophiles on the lithium azaenolates of 2-alkyl-2-oxazolines and 2-alkyl-2-thiazolines has been exa mined. This effect varies greatly, depending on the nature of the dielectro phile used. 3-Aminoindene (3) and 3-alkylidenephthalimidine (4-5) derivativ es were formed as a result of the reactions with dielectrophiles derived fr om ortho-substituted benzonitriles. Similarly, 2-alkylidenepyrrolidine (7) and 2-alkylidenepiperidine (8) derivatives were obtained in high yields fro m 2-alkyl-2-oxazolines or 2-alkyl-2-thiazolines and aliphatic dielectrophil es derived from omega -haloalkyldiphenylacetonitrile. C-C versus C-N annula tion reactions are discussed.